Cancer Procoagulant A (CPA), extracted from human and animal malignant tissue, was shown not to be a tissue thromboplastin, was inhibited by the diisopropylfluorophosphate (DFP), a serine protease inhibitor, and directly activated Factor X. The objectives of the proposed research are to purify CPA obtained from rabbit V2 carcinoma (CPA-V2) and to study its physical, chemical and enzymatic properties. The methods of purification will be an extension of those currently employed. The molecular weight of CPA will be determined by SDS-polyacrylamide gel electrophoresis, its isoelectric point by isoelectric focusing and its chemical composition by carbohydrates, lipid, and amino acid analysis. An antibody will be developed to the purified CPA-V2 by standard technique. The specificity of the antibody, its ability to inhibit CPA activity, and its cross reactivity with CPA obtained from human malignant tissue will be studied. CPA from several human malignant tissues will be purified and studied also. Comparison of the physicochemical and immunologic properties of the CPA from different malignant tissues will provide evidence as to the presence of CPA isozymes. An immunoassay for CPA will be developed to screen serum samples for purposes of diagnosis and treatment. Another objective in the proposed research is to determine whether CPA, a DFP sensitive serine protease (esterase), and/or fibrin, the product of CPA activity, has an effect on the growth of normal and malignant cells in culture. Preliminary studies showed that trypsin and CPA both stimulate the incorporation of H3-thymidine into DNA by cultured normal human fibroblasts. Changes in cell growth and cell surface membrane structure and function will be monitored by measuring the uptake of H3-thymidine into DNA, changes in cell number, labeled membrane proteins and glucose transport.